Means for neutralizing interfering disturbances



L. ESPENSCHIEI].

MEANS FOR NEUTRALIZING INTERFERING DISTURBANCES.

APPLICATION men nEc.5,19:a.

1,362,613. Patented Dec. 21,1920.

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1,362,613. Patented Dec. 21,1920.

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nngnn Patented Dec. 21,1920.

APPLICAUON FILED DECAL 191B.

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ATTORNEY L. ESPENSCHIED.

MEANS FOR NEUTRALIZING INTERFERING DISTURBANCES.

APPupATloN men on. 5. I918.

1,362,61 3, liatenced Dec. 21, 1920.

4 SHEETS-SHEET 4.

IN V EN TOR.

llayd/lspemmzkd A TTORNEY UNITED STATES PATENT OFFICE.

LLOYD ESPENSCHIED, O15 HOLLIS, NEW YORK, ASSIGNOR TO AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

MEANS FOR NEUTBALIZING INTERFERING DISTUBBANGES.

Specification of Letters Patent.

Patented Dec. 21, 1920.

Application filed December 5, 1918. Serial No. 265,456.

T 0 all whom it may concern.

Beit known that I, Imorn EsrnNsoi lnn, resiclng at H 0111s, Long Island,1n the county of Queens and State of New York, have invented certainImprovements in Means for Neutralizing Interfering Disturbances, ofwhich the following is a specification.

This invention relates to transmission circuits and more particularly tomeans for preventing interference where a plurality of transmissioncircuits parallel each other between two stations.

The invention has for one of its objects the provision of a neutralizingsystem which not only protects the transmission circuits from theeffects of foreign electrical systems but also avoids introducing anymutual interference between the said circuits, although other andfurther objects of the invention will more fully hereinafter appear.

Wherc a number of transmission circuits parallel each other interferingelectromotive forces may be set up in the circuits either due to mutualinduction between the circuits or to the disturbing action of someneighboring electric system such as a power circuit. The most commonsources of interference are traction or power systems operating onfrequencies of the order of fifteen to sixty cycles although lowfrequency telegraph circuits may also cause disturbing effects. Theselow frequency electromotive forces tend to interfere mostly with thecorresponding low frequency circuits of the transmission systems such asordinary telegraph circuits. The present invention therefore appliesespecially to the protection of low frequency circuits such as telegraphcircuits although it is of course not limited to this particularapplication.

It has been heretofore proposed to overcome interferences of thischaracter by means of neutralizing transformer system operating toimpose upon the affected circuits an electromotive force equal to andopposed to the original interfering electromotive force.- Ordinarilyforthe purposes of economy a neutralizing system including a singletransformer equipped with a plural-- ity of line windings is used forprotecting simultaneously a plurality of transmission circuits, one linewinding of the transformer being connected in each line wire of eachtransmission circuit and another line winding being connected in anauxiliary circuit which is subject to the same influence as regards thedisturbing source as the transmission circuits to be protected, theseline windings being assembled on a common transformer core and havingbetween them mutual inductance. In the usual case where the neutralizingsystem is designed for neutralizing low frequency induction the mutualinductance between the several line windings may be so large as to causemutual interference between the low frequency signaling channels.

It has been proposed in accordance with the patent to Shaw 1222810 ofApril 17, 1917 to overcome this difficulty by locating the neutralizingtransformer at or near the terminus of the circuits. The terminallocation of the transformer is frequently desirable not only because ofthe simplification of the problem of housing and maintenance, butfurthermore because in the case of the telegraph circuits composited ontelephone circuits where it is sometimes unnecessary to protect thetelephone channel, the transformer windings may be restricted to theMorse legs thereby avoiding the telephone loss which would be occasionedby their presence in the telephone circuit. This arrangement of thetransformer windings however introduces serious interference between theoutgoing currents of one channel and the weaker incoming currents ofanother channel. The interference due to incoming currents in onechannel imposing disturbing electromotive force upon incoming currentsof another channel, however is of small importance because the receivedcurrents are of such small magnitude as to produce unappreciableeffects. The present invention has particular reference to preventingthe introduction of interference of the first mentioned type viz.: thatbetween channels in which currents are being transmitted in oppositedirections.

The. objects of this invention are secured and the difiiculties abovereferred to are overcome by providing duplicate transformer arrangementsin both the line and the artificial line of the protected circuit. Oneline winding is included in each line wire and a corresponding windingis included in each artificial line circuit while the primary windingsof the transformer arrangement are included in the auxiliary orneutralizing circuit. In this way the mutual induction normally set upby the transformer between the real lines ofthe transmission circuits isbalanced with respect to the effect of outgoing upon incomingtransmission by an equivalent mutual induction between the artificiallines.

The invention will be more fully understood by reference to thefollowing descrip tion when read in connection with the accompanyingdrawings in which Figure 1 constitutes a circuit diagram showing thegeneral layout of the system in accordance with this invention; Fig. 2is a diagram illustratingthe invention as applied to a plurality oftelegraph circuits; Fig. 3 is a diagram illustrating the invention asapplied to telegraph circuits simplexed upon telephone lines; and Fig. 4is a diagrammatic representation of a systemembodying this invention asapplied to telegraph circuits superposed upon telephone circuits inaccordance with the well known composite system of telephony andtelegraphy.

Referring to. Fig. 1 three transmission lines L L and L are shownextending between two stations A and B the return conductors of thelines being-shown in dotted lines to indicate that either a metallic orground return may be used. Each line is provided with a transmitting andreceiving apparatus and a balancing artificial line at each station. Forinstance the line L is provided with transmitting arrangements T, and Tbridged across the junction points between the line and the balancingartificial lines N and N The receiving apparatus R and R at'the stationis connected across equal potential points in the line and artificialline with regard to the transmitting apparatus, equal inductance beinginchided between the terminals of the receiving apparatus and oneterminal of the transmitting apparatus. The arrangement as regards theline L and L is the same as that described with reference to line L andneed not be further discussed.

A foreign disturbing system paralleling the above described transmissioncircuits is indicated at L,.. In order to counteract the disturbingeffects of the system L a neutralizing circuit L is provided, saidcircuit paralleling the several transmission circuits so thatdisturbances are produced therein similar to those produced in thetransmission circuits. A neutralizing transformer L T including aplurality of windings is provided, one winding being included in each ofthe lines L L andL at station A while a primary winding is included inthe neutralizing circuit L. An equivalent transformer N T is alsoprovided at station A having an primary wind.- ing in the neutralizingcircuit L and line windings in circuit of each of the artificial lines NN and N Similarly at station B a neutralizing transformer L T isprovided for the lines and an equivalent transformer N T is provided forthe artificial lines.

The action of the balanced transformer arrangement above described inpreventing the introduction of cross-interferences be tween thetransmission circuits is as follows: Assuming that the transmittingapparatus T is sending, the arrows under the transformer windings inline L and artificial line N at station A indicate the instantaneousvalues and directions of flow of currents sent into the line andartificial line from the transmitter. The varying line current inducesthrough the line transformer a potentia and current in the line L asindicated by the arrow above the line winding in the line L at stationA. Similarly the varying artificial line current flowing through theartificial line N induces through the balanc ing transformer a potentialand current in the artificial line N as indicated by the arrows abovethe transformer winding of said circuit. These two induced currents areequal (by the symmetry of the systems and the identity of thetransformers) and mutually opposed with respect to the receivingapparatus R of the line L and consequently the receiving apparatus ofsaid line is un affected by the transmitting apparatus of the line L atthe same station.

Similar balanced relations obtain between all other combinations ofcircuits within the group. This balance between sending and receivingchannels of different circuits at at the same station is obtained at theexpense of an increased unbalanced mutual inductance between similarlydirected channels. This is permissible however since interfere fcrencebetween receiving channels is usually negligibly small. The action inthis respect may be understood by reference to station B. The arrowsbeneath the transformer windings of the line L and the artificial lineN, at said station indicate the value and direction of the currentflowing due to the action of the transmitter T at station A. Thesecurrents induce potentials and currents in the line L and artificialline N as indicated by the arrows above the windings of the transformersin said circuits. It will be seen that the interfering currents in theline and artificial line do not oppose each other so that theinterference between currents received at the same station is increased.Owing to the small magnitude of the received currents however thisresult while undesirable is of little consequence.

That the balancing arrangement of the neutralizing system does notsacrifice the necessary action of neutralizing foreign disturbingelectromotive forces from the circuit L may be shown as follows withreference to the drawing of Fig. 1. Assume the interfering electromotiveforces impressed upon all circuits of the group to be E. Thiselectromotive force divides equally between the primary windings ofmerged into one transformer.

the four equal transformers in the circuit L... For simplicity inexplanation the line voltage drop will be neglected. Then a l voltage 35is impressed across each of the four windings as indicated. This istransformed to an equal counter-electromotive force The remainingone-half on the drawing) is then neutralized with respect to its effectupon the receiving apparatus of the transmission circuits by thecounter-electromotive forces set up by the balancing transformer E! El(15 011 the drawing). The condition of neutralization is therefore onein which the line transformers neutralize one-half and the artificialline balancing transformers the other one-half of the; disturbingelectromotive force.

The line and balancing transformer may be combined upon a common coreand made to be physically a single unit. This consolidation is indicatedin Fig. 2, in which trans formers l. T and. L T are provided withwindings in both the line and the artificial line side of eachtransmission circuit. Here the transmission circuits L L and L areillustrated as ordinary ground return duplex telegraph circuits. Theline and balancing windings for both the telegraph circuits (thesecondaries of the neutralizing system) and the primary neutralizingcircuit are The two windings of each circuit are connected mutual seriesaiding around the interference current path so that they comb-inc inneutralizing the interfering electromotive force from the disturbingcircuit L They are mutually opposed to transmitted telegraph currentsand thereby prevent the latter from interfering with the receivedcurrents of other circuits. This arrangement is not only more economicalfrom a. cost standpoint but is better from a telegraph standpointbecause it facilitates obtaining and maintaining the duplex balance, bycausing changes in the elfectiveimpedance of the across each of thesecondary windtransformers resulting from saturation effects, to affectalike the line and balancing line sides of the circuits. windingspresent less inductance to the outgoing telegraph currents by virtue oftheir close and mutually opposed coupling. The arrangement is alsobetter from the stand point of the neutralization action of thetransformers since saturation effects in the transformers due to Morsecurrents and the resulting reduction of neutralization efficiency areavoided.

Fig. 3 illustrates a similar arrangement as applied to telegraphcircuits superposed on telephone circuits by a simplex arrangement. Inthe drawing L and L represent tele phone lines extending between twostations A and B where they are connected to their terminal arrangementsthrough transformers of the well known phantom type. Morse legs 1 and 2are connected to midpoints of the windings of the transformers in linesL and L at station A. Similarly Morse legs 11 and 22 are connected tothe midpoints of the transformers at station B. The Morse legs terminatein the usual duplex telegraph sets including artificial lines N N N andN Athirdtelephone circuitL similar in all respects to the telephonecircuits L and L is provided with ground taps X and X connected to themidpoints of the windings of the terminal transformers. This circuitfunctions as the neutralizing circuit of the system as it is related tothe disturbing system L in a manner similar to that of the lines L, andL Neutralization transformers L T and L T are provided, the formerhaving secondary windings in each of the Morse legs and each of theartificial line circuits at station A and a primary winding in theground tap X. In a similar manner the transformer L T has secondarywindings in the Morse legs and artificial line circuits at station Bwhile its primary winding is in the ground tap X. The operation of thiscircuit so far as prevention of interference is concerned is in allrespects similar to that of Fig. 2 and. need not be further described.

Fig. 4 illustrates the invention as applied to telegraph circuitssuperimposed upon telephone circuits by compositing the circuits. Inthis figure telephone line L terminates at stations A and B in jacks Jand J Telegraph legs 1 and 2 are led from each of the line wires of thetelephone circuit at station A, similar legs 11 and 22 being led fromthe line wires of the telephone circuit at station B. Each of thetelephone legs terminates in the usual duplex telegraph sets includingtransmitters, receivers and artificial lines as indicated. Included inthe legs 1 and 2 are inductances 3 and 4 to prevent a flow of highfrequency talking current to the Morse legs, similar induc tances 33 and44 being included in the Morse Furthermore the legs 11 and 22.Capacities 5, 6, 55 and 66 are shunted to ground beyond the inductancesto form by-passes for any telephone currents which may be transmittedthrough the inductances. Condensers 7 and 8,77 and 88 are inserted inthe telephone conductors beyond the Morse legs said condensers being soproportioned as to permit the passage of the relatively high frequencytelephone currents and prevent the passage of low frequency Morsecurrents. to ground any Morse currents which may pass through thecondensers ground taps 9 and 99 including capacity and inductances areprovided. Another telephone circuit L may be used as the neutralizingcircuit and for this purpose connections X and X similar to thosedescribed in Fig. 3 are provided. Neutralizing transformers L T and L Tare arranged with secondary windings in the various Morse legs andartificial line circuits and primary windings in the ground taps X andX. The operation. of this circuit with regard to neutralization ofdisturbing electromotive forces therein either from systems of the samecharacter or from foreign electrical systems is the same as that alreadydescribed in connection with Fig. 2 and need not be further discussed.

By means of the arrangements above described a simple and yet efficientmeans is provided for neutralizing interfering electromotive forces andwhile the invention has been shown embodied in certain specificorganizations it will be obvious that the general principles hereindisclosed may be em bodied in many other organizations widely differentfrom those illustrated without departing from the spirit of theinvention as defined in the following claims.

What is claimed is:

1. In a transmission system, a transmission circuit, a source ofsignaling current therefor, a balancing circuit therefor, a source ofdisturbing electromotive force independent of said signaling source, athird source for counteracting said disturbingapparatus, a source ofdisturbing electromotive force independent of said signaling source,fifthlld source for-counteractmg sald In order to shunt disturbingsource, said third source being inductively related to both saidtransmission circuit and said balancing circuit.

4. In a transmission system, a plurality of transmission circuits,balancing circuits for each transmission circuit, a disturbing source ofelectromotive force, an auxiliary circuit for counteracting saiddisturbing source, lumped mutual impedances in said transmissioncircuits and auxiliary circuit, and lumped mutual impedances in saidauxiliary circuit and balancing circuits for simulating said firstmentioned impedances.

5. In a transmission system, a plurality of transmission circuits,sources of signaling current therefor, balancing circuits for eachtransmission circuit, an auxiliary circuit, a source independent of saidsignaling sources for producing disturbing electromotive forces in saidtransmission circuits and counteracting electromotive forces in saidauxiliary circuit, said auxiliary circuit being inductively related tosaid transmission circuits and balancing circuits.

6. Ina transmission system, a plurality of transmission circuitsinterconnecting two stations, transmitting and receiving apparatus foreach circuit at each station, a balancing circuit at each station foreach transmission circuit to render the receiving apparatus of any lineat each station unresponsive to the transmitting apparatus of said linethereat, lumped mutual impedances for said transmission circuits, andlumped mutual impedances for said balancing circuits simulating those ofthe transmission circuits, whereby the transmitting apparatus of anytransmission circuit at a given station is without effect upon thereceiving apparatus of other transmission circuits at that station.

7. In a transmission system, a plurality of transmission circuitsinterconnecting two stations, transmitting and receiving apparatus foreach circuit at each station, a balancing circuit at each station foreach trans mission circuit to render the receiving apparatus of any lineat each station unresponsive to the transmitting apparatus of said linethereat, an auxiliary circuit, a disturbing source independent of saidtransmitting and receiving apparatus for producing disturbingelectromotive forces in said transmission circuits and counteractingdisturbances in said auxiliary circuit, and mutual inductive connectionsbetween said auxiliary circuit and said transmission and balancingcircuits, whereby the disturbing effects in said transmission circuitsare counteracted and the transmitting apparatus of any transmissioncircuit at a given station is Without effect upon the receivingapparatus of other transmission circuits at that station.

8. In a transmission system, a telephone circuit, a telegraph circuitsuperposed thereon,'a s'ourceyof signaling currenttherefor, a...

balancing circuit for said telegraph circuit, a source of disturbingelectromotive force independent of said signaling source, a third sourcefor counteracting said disturbing source, said third source beinginductively related to said telegraph circuit and balancing circuitexternal to the telephone circuit.

9. In a transmission system, a plurality of telephone circuits,telegraph circuits superposed thereon, balancing circuits for saidtelegraph circuits, lumped mutual impedances for said telegraph circuitsexternal to said telephone circuits, and lumped mutual iinpedances forsaid balancing circuits simulating those of the telegraph circuits.

10. In a transmission system, a plurality of telephone circuitsextending between two stations, telegraph circuits superposed there on,transmitting and receiving apparatus for each telegraph circuit at eachstation, a balancing circuit for each telegraph circuit whereby thereceiving apparatus of any telegraph circuit at a given station isrendered unresponsive to the transmitting apparatus of said circuitthereat, an auxiliary circuit, a disturbing source independent of saidtransmitting and receiving apparatus for producing disturbingelectromotive forces in said telegraph circuits and counteractingelectromotive forces in said auxiliary circuit, mutual inductiveconnections between said auxiliary circuit and said telegraph circuitsexternal to said telephone circuits and similar mutual inductiveconnections between said auxiliary circuit and said balancing circuits,whereby the disturbing eiiects in said telegraph circuits arecounteracted and the transmitting apparatus of any telegraph circuit ata given station is without eifect upon the receiving apparatus of othertelegraph circuits at that station.

In testimony whereof I have signed my name to this specification thistwenty-seventh day of November, 1918.

LLOYD ESPENSCI-IIED.

